Emissions from cement production on the environment and health



Pollution has become a real major problem in the world. Emissions from cement manufacturing are one of the main contributors to global warming and climate change. Cement manufacturing is a very energy intensive process, which involves intensive fuel consumption for the manufacture of clinker and results in emissions..But the cement industry is an energy enormous intensive and products many emissions, odors and noise. The emissions from cement plants which cause greatest concern and which need to be dealt with are dust, carbon dioxide CO2, nitrogen oxides (NOx) and sulphur dioxide (SO2).

This article deals with the review of the main environmental issues related to the cement production and her impact in the health.

Keywords: cement, emissions, environmental impact, health impacts.

It is impossible to envisage a modern life without cement. Cement is an extremely important construction material used for housing and infrastructure development and a key to economic growth. Cement demand is directly associated to economic growth and many growing economies are striving for rapid infrastructure development which underlines the tremendous growth in cement production [1].

In Europe the use of cement and concrete (a mixture of cement, aggregates, sand and water) in large civic works can be traced back to antiquity. In 2008 there were 268 installations producing cement clinker and finished cement in the European Union with a total of 377 kilns [2].

Raw material and Energy consumption result in emissions to air which include dust and gases. The exhaust gases from a cement kiln contains are nitrogen oxides (NOx), carbon dioxide, water, oxygen and small quantities of dust, chlorides, fluorides, sulfur dioxide, carbon monoxide, and still smaller quantities of organic compounds and heavy metals [3].These emissions are not only deteriorating air quality but also degrading human health. Emissions have local and global environment impact resulting in global warming, ozone depletion, acid rain, biodiversity loss, reduced crop productivity etc [4].

Emissions to air and noise emissions arise during the manufacture of cement. Furthermore with regard to the use of waste, odors can arise, e.g. from the storage and handling of waste. In this section, ranges of air pollutant emissions are presented for the process of cement production, including other process steps, such as the storage and handling of, e.g. raw materials, additives and fuels including waste fuels.

The most significant environment health and safety issue of cement manufacturing is emission [5]. Cement industry is potential anthropogenic source of air pollution. It has estimated that cement production originates about 5 % of global manmade CO2 emissions [6].There are many other sources of emissions from cement manufacturing, such as emissions from transportation equipment used in the mining and transporting raw and finished material, fuel used for electricity production for operating other process in cement manufacturing [7]

Air pollution from Cement manufacturing is becoming an environmental problem worldwide. Recent studies determine relationship between cement air pollution and human health diseases(pneumonia; cancers etc). Pollutants from cement plants are causing harmful effects on human health and environment [6,6].

Oxides of sulphur are formed from the combustion of fuels which contain sulphur and oxidation of sulphur containing raw material [8]. Sulfur is present in all cement raw materials. SO ₂ Emissions generated from sulphur in the raw materials are lesser than SO ₂ emissions generated from sulfur in the fuel [9]. In rotary kiln raw material oxidized to form SO ₂ and SO ₃ at temperature between 3700 C and 4200 C prevailing in the kiln preheater [10]. Sulfur dioxide (SO ₂ ) is formed by thermal decomposition of calcium sulfate in clinker. SO ₃ is present as anhydrite and can easily be decomposed to SO ₂ and O ₂ . But the highly alkaline condition in the kiln can absorb 90 % of the sulphur oxides. Sox emission can be controlled by using low slphur fuel and raw material.

We are witnessing the emission of several gases during the production of cement.

The sulfur oxides react with water vapor and other chemicals high in the atmosphere in the presence of sunlight to form sulfuric acids. The acids formed usually dissolve in the suspended water droplets, which can be washed from the air on to the soil by rain or snow. This is known as acid rain. It is responsible for so much damage to life and health. Respiratory illnesses such as bronchitis are seen to increase with sulfur oxide levels [11]. Increased level of SOx in the atmosphere can also degrade agricultural productivity and death of some plants.The sulfur oxide emission process is explained in the table below

Nitrogen oxides are produced in the combustion flame of a rotary kiln, which enter the atmosphere with the exit gases, and undergo many reactions in the atmosphere. Majorly NOx are formed by thermal oxidation, which happens in temperature range between 1,200–1,600 °C. Due to high temperature significant amounts of thermal NO are generated in the Kiln. Combustion of nitrogen-bearing fuels such as certain coals also produces N ₂ , or NO. [12].

N ₂ + O → NO + N

N + O ₂ → NO + O

As temperature increases, NO formation also increases. About 90 % of the nitrogen oxides are produced in the form of nitric oxide (NO) and the remaining 10 % are in the form of nitrogen dioxide (NO ₂ ) [11,10].

Produced NO converts to NO ₂ at the exit of the stack at atmospheric conditions and appears in brown-yellow color.

NO + ½ O ₂ → NO ₂ [9,40].

NOx causes a wide variety of health and environmental impacts because of various compounds and derivatives in the family of nitrogen oxides, including nitrogen dioxide, nitric acid, nitrous oxide, nitrates, and nitric oxide.

Similar to sulphur dioxide, NOx react with water and other compounds to form various acidic compounds. When these acidic compounds that are deposited to the earth’s surface, they can impair the water quality of different water bodies and acidify lakes and streams. Acidification (low pH) and the chemical changes result in making it difficult for some fish and other aquatic species to survive, grow, and reproduce. Acid rain can also harm forest ecosystems by directly damaging plant tissues [13].

Nitrous oxide is a greenhouse gas and it accumulates in the atmosphere with other greenhouse gasses causing a gradual rise in the earth's temperature. This will lead to global warming and climate change. NOx and volatile organic compounds react in the atmosphere in the presence of sunlight to form ground-level ozone, which causes smog in cities and rural areas. This ground level ozone when breathed, it causes respiratory disease and other health problems. Nitrogen dioxide affects body functions such as difficulty in breathing, chronic lung diseases, such as chronic inflammation and irreversible structural changes in the lungs, which with repeated exposure, can lead to premature aging of the lungs and other respiratory illness. Studies indicate positive relation between nitrogen dioxide concentrations and heart disease and cancer cases [11,22].

Cement industry is a major source of CO ₂ emission. CO ₂ is emitted from the calcinations process of limestone and from combustion of fuels in kiln. It estimates that half of the CO ₂ is generated from fuel combustion and half originates from decarbonization of raw material. An indirect source of CO ₂ and other pollutant in cement production is from consumption of electricity, assuming that the electricity is generated from fossil fuels.

CaCO ₃ → Cao + CO ₂

(1 kg 0.56 kg + 0.44 kg) [12,20]

MgCO ₃ → MgO + CO ₂ [9,18]

The amount of CO ₂ released in calcination can be calculated from the component formula weight ratios for of limestone [14]. CO ₂ emissions from different fuels combustion can be calculated from emission factors of fuels defined by the Inter government Panel on Climate Change (IPCC). The amount of CO ₂ emission during this process is directly related to the type of fuel used like coal, fuel oil, pet coke, natural gas, alternate fuel. Typically, kiln is fueled with coal as other fossil fuels are too expensive to be used in cement production. However carbon based waste material such as tires are commonly used in cement kiln to use its energy content.

Process-related CO ₂ emissions from cement production are the second largest source of industrial CO ₂ emissions in the United States. A number of studies have suggested that, the cement industry contributes about 5 % of total anthropogenic CO ₂ emissions, worldwide [15]. It has long been known that carbon dioxide emissions contribute to climate change. Constantly increasing CO ₂ emissions are responsible for an increase in temperatures, which is expected to continue over the coming decades reaching up to +1.4˚ to +5.8˚C globally by the year 2100. Increasing temperature can cause severe droughts in some parts of the world, extreme weather conditions, the loss of ecosystems and potentially hazardous health effects for people [16].

Recent study details the impact of increase of temperature by carbon dioxide, the resulting air pollution would lead annually to about a thousand additional deaths and many more cases of respiratory illness and asthma in the United States. It also shows that fossil fuel CO ₂ increases surface ozone, carcinogens and particulate matters resulting in increase cases of asthma, death, hospitalization and cancer cases [17]. CO can cause harmful health effects by reducing oxygen delivery to the body's organs and tissues, as well as adverse effects on the cardiovascular and central nervous systems. CO can also contributes to the formation of smog (ground-level ozone), which can cause respiratory problems.

Emissions of CO ₂ from the cement manufacturing sector can be reduced by improving the energy efficiency of the process, adopting more efficient process, switching to low carbon fuel from high carbon fuels, using alternate fuels such as biomass, reducing clinker to cement ratio, removing CO ₂ from the flue gases.

It is well known fact that air pollution is hazardous to environment and human health. Due to infrastructure developmental activities cement industry is flourishing and resulting in the environmental deterioration and in turn degradation of the human health worldwide. The gaseous and particulate emissions from cement plants are degrading air quality and thus creating considerable environmental pollution especially air pollution [18].

Through these studies and previous research we can conclude that the cement industry causes enormous damage to ecology and human health. The main environmental and health concerns have identified a significant amount of fine dust and gas emissions. Exposure of workers and communities to dust emissions is associated with many health problems. For sustainable development, the world should focus on effective emission control technology

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